Investigation on the Corrosion Behavior of Nickel‐Base Alloys in Molten Chlorides for Sensible Heat Energy Applications. Issue 7 (20th April 2020)

• Record Type: Journal Article
• Authors: Knosalla, Christian; Lau, Marius; Schmies, Lennart; Lippmann, Wolfgang; Hurtado, Antonio
• Is Part Of: Advanced engineering materials. Volume 22:Issue 7(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-04-20
• Subjects: concentrated solar power -- heat-transfer fluids -- high-temperature corrosion -- molten chlorides -- molten salts; Materials -- Periodicals; 620.11
• DOI: 10.1002/adem.202000099
• Languages: English
• ISSNs: 1438-1656

Abstract

Abstract : Nine selected alloys are exposed in molten KCl–LiCl (eutectic composition) at 1073 K for 167 h under argon atmosphere to predict the long‐term corrosion behavior of these structural materials. The corrosive attack of each alloy is assessed with gravimetric methods, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy measurements. The corrosion rate of each alloy is calculated in accordance with ASTM G1‐03. Low chromium containing alloys as HAYNES 242, Hastelloy B‐3, and Hastelloy N revealed minor or no significant corrosive attack after molten chloride exposure. Alloy 600, Alloy 617, HAYNES 625, Hastelloy X, HAYNES 230, and HAYNES 188 with a chromium content w Cr > 8% show severe corrosive attack with complete chromium depletion along the near‐surface layer and partially along grain boundaries. The results show that chromium forms chromium oxide with impurities of oxygen and water vapor at low oxygen partial pressures. This initiates an accelerated corrosion of the alloying elements in the matrix of Ni, Cr, Mo, Fe, and Co, due to chlorine formation. The influence of the composition of nickel‐base alloys on the corrosion resistance is discussed based on the comparison of the gravimetric measurements and thermodynamic calculations. Abstract : This study investigates the corrosion behavior of nine nickel‐base alloys in KCl–LiCl at equal test conditions. This enables a comparison of the corrosion resistance of structural materials for the application of molten chlorides as high‐temperature heat‐transfer fluids and allows an in‐depth consideration for the development of novel alloy compositions or plating strategies to decrease corrosion rates.